package com.lagou.edu.mvcframework.servlet;

import com.lagou.edu.mvcframework.annotations.*;
import com.lagou.edu.mvcframework.pojo.Handler;
import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.StringUtils;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Parameter;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * @author 13771
 * @date 2020/8/7 22:23
 * @description
 */
public class LgDispatcherServlet extends HttpServlet {
    private Properties properties = new Properties();

    List<String> classNames = new ArrayList<>();  //缓存扫描到的类的全限定类名

    //ioc容器
    private Map<String,Object> ioc = new HashMap<>();

    //handlerMapping
    //private  Map<String ,Method> handlerMapping = new HashMap<>(); //存储url和method之间的映射关系
    private  List<Handler> handlerMapping = new ArrayList<>();

    @Override
    public void init(ServletConfig config) throws ServletException {
        //1.加载配置文件 springmvc.properties
        String contextConfigLocation = config.getInitParameter("contextConfigLocation");
        doLoadConfig(contextConfigLocation);


        //2.扫描相关的类，扫描注解
        doScan(properties.getProperty("scanPackage"));

        //3.初始化Bean对象(实现IOC容器，基于注解)
        doInstence();

        //4.实现依赖注入
        doAutowired();

        //5.构造一个HandlerMapping处理器映射器，将配置好的url和Method建立映射关系
        initHandlerMapping();

        System.out.println("lagou mvc 初始化完成。。。");
    }

    //构造一个HandlerMapping处理器映射器
    private void initHandlerMapping() {
        if (ioc.isEmpty()) return;

        for (Map.Entry<String,Object> entry:ioc.entrySet()){
            //获取ioc中当前遍历的对象的class类型
            Class<?> aClass = entry.getValue().getClass();

            if (!aClass.isAnnotationPresent(LagouController.class)){continue;}

            String baseUrl = "";
            if (aClass.isAnnotationPresent(LagouRequestMapping.class)){
                LagouRequestMapping annotation = aClass.getAnnotation(LagouRequestMapping.class);
                baseUrl = annotation.value();
            }

            //获取方法
            Method[] methods = aClass.getMethods();
            for (int i = 0; i < methods.length; i++) {
                Method method = methods[i];
                if (!method.isAnnotationPresent(LagouRequestMapping.class)){continue;}

                LagouRequestMapping annotation = method.getAnnotation(LagouRequestMapping.class);
                String methodUrl = annotation.value();
                String url = baseUrl + methodUrl;

                //把method所有信息及url封装成一个Handler
                Handler handler = new Handler(entry.getValue(),method, Pattern.compile(url));

                //计算方法的参数位置信息
                Parameter[] parameters = method.getParameters();
                for (int j = 0; j < parameters.length; j++) {
                    Parameter parameter = parameters[j];
                    if (parameter.getType() == HttpServletRequest.class || parameter.getType() == HttpServletResponse.class){
                        handler.getParamIndexMapping().put(parameter.getType().getSimpleName(),j);
                    }else{
                        handler.getParamIndexMapping().put(parameter.getName(),j);
                    }
                }

                //建立url和method之间的映射关系
                handlerMapping.add(handler);

            }
        }
    }

    //实现依赖注入
    private void doAutowired() {

        if (ioc.isEmpty()) return;

        //ioc中有对象，再进行依赖注入处理
        //遍历ioc中所有对象，查看对象中的字段是否有@LagouAutowired注解，如果有则需要维护依赖注入关系
        for (Map.Entry<String,Object> entry:ioc.entrySet()){
            //获取bean对象中的字段信息
            Field[] declaredFields = entry.getValue().getClass().getDeclaredFields();
            for (int i = 0; i < declaredFields.length; i++) {
                Field declaredField = declaredFields[i];
                if (!declaredField.isAnnotationPresent(LagouAutowired.class)){
                    continue;
                }

                //有该注解
                LagouAutowired annotation = declaredField.getAnnotation(LagouAutowired.class);
                String beanName = annotation.value();  //需要注入的bean的id
                if ("".equals(beanName.trim())){
                    //没有配置具体的bean id ,那就需要根据当前字段类型注入(接口注入)
                    beanName = declaredField.getType().getName();
                }

                //开启赋值
                declaredField.setAccessible(true);
                try {
                    declaredField.set(entry.getValue(),ioc.get(beanName));
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                }
            }

        }
    }

    //IOC容器
    //基于classNames缓存的类的全限定类名，以及反射技术，完成对象创建和管理
    private void doInstence() {
        if(classNames.size() == 0) return;

        try{

            for (int i = 0; i < classNames.size(); i++) {
                String className = classNames.get(i);

                //反射
                Class<?> aClass = Class.forName(className);
                //区分controller  区分service
                if (aClass.isAnnotationPresent(LagouController.class)){
                    //controller的id此处不做过多处理，不取value属性了，直接拿类的首字母小写作为id,保存到ioc中
                    String simpleName = aClass.getSimpleName();
                    String lowerFirstSimpleName = lowerFirst(simpleName);
                    Object o = aClass.newInstance();
                    ioc.put(lowerFirstSimpleName,o);
                }else if (aClass.isAnnotationPresent(LagouService.class)){
                    LagouService annotation = aClass.getAnnotation(LagouService.class);
                    //获取注解value值
                    String beanName = annotation.value();
                    //如果指定了id,就以指定的为准
                    if (!"".equals(beanName.trim())){
                        ioc.put(beanName,aClass.newInstance());
                    }else {
                        //如果没有指定，就以类名首字母小写
                        beanName = lowerFirst(aClass.getSimpleName());
                        ioc.put(beanName,aClass.newInstance());
                    }

                    //service层往往是有接口的，面向接口开发，此时再以接口名为id,放入一份对象到ioc中，便于后期根据接口类型注入
                    Class<?>[] interfaces = aClass.getInterfaces();
                    for (int j = 0; j < interfaces.length; j++) {
                        Class<?> anInterface = interfaces[j];
                        //以接口的全限定类名作为id放入ioc中
                        ioc.put(anInterface.getName(),aClass.newInstance());
                    }
                }else {
                    continue;
                }

            }
        }catch (Exception e){
            e.printStackTrace();
        }

    }

    //首字母小写方法
    public String lowerFirst(String str){
        char[] chars = str.toCharArray();
        if ('A' <= chars[0] && chars[0] <= 'Z'){
            chars[0] +=32 ;
        }
        return String.valueOf(chars);
    }

    //扫描类
    private void doScan(String scanPackage) {
        String scanPackagePath = Thread.currentThread().getContextClassLoader().getResource("").getPath() + scanPackage.replaceAll("\\.", "/");
        File pack = new File(scanPackagePath);

        File[] files = pack.listFiles();
        for(File file : files){
          if (file.isDirectory()){
              //递归
              doScan(scanPackage + "." + file.getName());
          }else if (file.getName().endsWith(".class")){
              String className = scanPackage + "." +file.getName().replaceAll(".class","");
              classNames.add(className);
          }
        }
    }

    //加载配置文件
    private void doLoadConfig(String contextConfigLocation) {

        InputStream resourceAsStream = this.getClass().getClassLoader().getResourceAsStream(contextConfigLocation);
        try {
            properties.load(resourceAsStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //根据uri 获取到能够处理当前请求的handler(从handlerMapping中)
        Handler handler = getHandler(req);
        if (handler == null){
            resp.getWriter().write("404 not found");
            return;
        }

        //增加权限判断功能

        //判断Controller类是否有@LagouSecurity注解
        if (handler.getController().getClass().isAnnotationPresent(LagouSecurity.class)){
            LagouSecurity annotation = handler.getController().getClass().getAnnotation(LagouSecurity.class);
            String[] value = annotation.value();
            String username = req.getParameter("username");
            if (value.length > 0 ){
                if (!ArrayUtils.contains(value,username)){
                    resp.setHeader("Content-type", "text/html;charset=UTF-8");
                    resp.setCharacterEncoding("UTF-8");
                    resp.getWriter().write(username+"无访问权限！");
                    return;
                }
            }
        }
        //判断Controller类中的方法是否有@LagouSecurity注解
        if (handler.getMethod().isAnnotationPresent(LagouSecurity.class)){
            LagouSecurity annotation = handler.getMethod().getAnnotation(LagouSecurity.class);
            String[] value = annotation.value();
            String username = req.getParameter("username");
            if (value.length > 0 ){
                if (!ArrayUtils.contains(value,username)){
                    resp.setHeader("Content-type", "text/html;charset=UTF-8");
                    resp.setCharacterEncoding("UTF-8");
                    resp.getWriter().write(username+"无访问权限！");
                    return;
                }
            }
        }



        //参数绑定
        //获取所有参数类型数组，这个数组的长度就是我们最后要传入的args数组的长度
        Class<?>[] parameterTypes = handler.getMethod().getParameterTypes();

        //根据上述数组长度创建一个新的数组(参数数组，是要传入反射调用的)
        Object[] paramValues = new Object[parameterTypes.length];

        //以下就是为了向参数数组中塞值，而且还得保证参数的顺序和方法中形参顺序一致
        Map<String, String[]> parameterMap = req.getParameterMap();

        //遍历request中所有参数  （填充除了request,response之外的参数）
        for (Map.Entry<String,String[]> param : parameterMap.entrySet()){
            String value = StringUtils.join(param.getValue(), ",");

            //如果参数和方法中的参数匹配上了，填充数据
            if (!handler.getParamIndexMapping().containsKey(param.getKey())){continue;}

            //方法形参确实有该参数，找到它的索引位置，
            Integer index = handler.getParamIndexMapping().get(param.getKey());

            paramValues[index] = value;  //前端传递过来的参数值填充到paramValues对应的位置上
        }

        Integer requestIndex = handler.getParamIndexMapping().get(HttpServletRequest.class.getSimpleName());
        paramValues[requestIndex] = req;

        Integer responseIndex = handler.getParamIndexMapping().get(HttpServletResponse.class.getSimpleName());
        paramValues[responseIndex] = resp;


        //最终调用handler的method属性
        try {
            handler.getMethod().invoke(handler.getController(),paramValues);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }


    }

    private Handler getHandler(HttpServletRequest req) {
        if (handlerMapping.isEmpty()){return null;}


        String requestURI = req.getRequestURI();
        for (Handler handler:handlerMapping){
            Matcher matcher = handler.getPattern().matcher(requestURI);
            if (!matcher.matches()){continue;}
            return handler;
        }

        return null;
    }


}
